Nuclear magnetic resonance (NMR) sensors, such as gyroscopes and magnetometers, employ optical beams to operate, such as to detect rotation about a sensitive axis or to detect the presence and magnitude of an external magnetic field. As an example, an NMR sensor system can employ a first optical beam as a pump beam. For example, the pump beam can be a circularly-polarized optical beam that is configured to spin-polarize an alkali metal vapor, such as cesium (Cs) or rubidium (Rb), within a sealed cell of the sensor. The NMR sensor system can also employ a second optical beam as a probe beam. For example, the probe beam can be a linearly-polarized optical beam that is configured to indirectly detect precession of noble gas isotopes, such as xenon (Xe), based on the directly measured precession of the alkali metal, such as for detecting rotation of the detection system about the sensitive axis or detecting the magnitudes of the external magnetic field.